1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device whereby a thermally oxidized film having a relatively large thickness is removed from or formed on primarily an SOI wafer. For example, the method is used to remove an oxide film mask for forming a well or used to form a LOCOS oxide film, etc.
2. Background Art
Japanese Laid-Open Patent Publication No. H10-173041 discloses a technique in which a trench isolation semiconductor substrate with polysilicon-filled trenches is formed in such a manner as to minimize warping of the substrate. Specifically, when filling the trenches of the substrate with polysilicon, this prior art technique also forms a polysilicon film on a silicon oxide film formed on the bottom surface of the substrate so that the silicon oxide film is protected by the polysilicon film.
If a substrate with a large amount of warpage is used to manufacture a semiconductor device, the substrate may suffer from various process failures such as exposure failure in photolithography, suction attachment failure to the stage, and transfer failure on the manufacturing line. For example, if a thick oxide film such as a LOCOS oxide film is formed only on the top surface side of a substrate, the substrate tends to warp. Further, a thick oxide film mask used, e.g., for forming a well in a substrate tends to cause the substrate to warp.